can't add the string *.pdf* anywhere in the body

I've been trying without success to add a certain content and when hitting submit, it goes to a 404 page no found.

I tried as different content types, and I tried pasting that content to an existing node.

After careful dissection of the content itself, I figured that my drupal install somehow doesn not allow me to have anything with .pdf in the body, be it a link or just plain .pdf on the text.

If I edit an existing content, then add the pdf. drupal says the content was edited by the body remains the same...doesn't get changed.

Anybody have any idea why it would be filtering .pdf on the body?

thanks in advance.